Supported polymerisation catalysts

ABSTRACT

A method for the preparation of a supported transition metal catalyst system which includes the steps of: (i) mixing together in a suitable solvent (a) an aluminoxane and (b) an ionic activator containing a cation and an anion, wherein the anion has at least one substituent containing a moiety having an active hydrogen, (ii) addition of the mixture from step (i) to a support material, and (iii) addition of a transition metal compound in a suitable solvent. The use of tetraisobutylaluminoxane as the aluminoxane results in a more stable activity profile and improved polymer properties in particular melt strength.

The present invention relates to supported catalysts suitable for thepolymerisation of olefins and in particular to supported metallocenecatalysts providing advantages for operation in gas phase processes.

In recent years there have been many advances in the production ofpolyolefin homopolymers and copolymers due to the introduction ofmetallocene catalysts. Metallocene catalysts offer the advantage ofgenerally a higher activity than traditional Ziegler catalysts and areusually described as catalysts which are single site in nature.

There have been developed several different families of metallocenecomplexes. In earlier years catalysts based on bis (cyclopentadienyl)metal complexes were developed examples of which may be found in EP129368 or EP 206794. More recently complexes having a single or monocyclopentadienyl ring have been developed. Such complexes have beenreferred to as ‘constrained geometry’ complexes and examples of thesecomplexes may be found in EP 416815 or EP 420436. In both of thesecomplexes the metal atom eg. zirconium is in the highest oxidationstate.

Other complexes however have been developed in which the metal atom maybe in a reduced oxidation state. Examples of both the bis(cyclopentadienyl) and mono (cyclopentadienyl) complexes have beendescribed in WO 96/04290 and WO 95/00526 respectively.

The above metallocene complexes are utilised for polymerisation in thepresence of a cocatalyst or activator. Typically activators arealuminoxanes, in particular methyl aluminoxane or compounds based onboron compounds. Examples of the latter are borates such astrialkyl-substituted ammonium tetraphenyl- or tetrafluorophenyl-borates.Catalyst systems incorporating such borate activators are described inEP 561479, EP 418044 and EP 551277.

The above metallocene complexes may be used for the polymerisation ofolefins in solution, slurry or gas phase. When used in the gas phase themetallocene complex and/or the activator are suitably supported. Typicalsupports include inorganic oxides eg. silica or polymeric supports mayalternatively be used.

Examples of the preparation of supported metallocene catalysts for thepolymerisation of olefins may be found in WO 94/26793, WO 95/07939, WO96/00245, WO 96/04318, WO 97/02297 and EP 642536.

WO 98/27119 describes supported catalyst components comprising ioniccompounds comprising a cation and an anion in which the anion containsat least one substituent comprising a moiety having an active hydrogen.In-this disclosure supported metallocene catalysts are exemplified inwhich the catalyst is prepared by treating the aforementioned ioniccompound with an organometallic compound such as triethylaluminium (TEA)followed by subsequent treatment with the support and the metallocene.

Among the organometallic compounds disclosed in WO 98/27119 arealuminoxanes, in particluar methyl aluminoxane (MAO) although no furtherdetails nor exemplification of such compounds is described.

WO 99/28353 describes similar catalyst systems comprising anionscontaining active hydrogens which are also contacted withtrialkylaluminium compounds.

We have now surprisingly found that the use of aluminoxanes as theorganometallic compound has particular advantages relating to theactivity profile of the resultant supported transition metal catalysts.

Thus according to the present invention there is provided a method forthe preparation of a supported transition metal catalyst system saidmethod comprising the steps of:

(i) mixing together in a suitable solvent

-   -   (a) an aluminoxane and    -   (b) an ionic activator comprising a cation and an anion wherein        the anion has at least one substituent comprising a moiety        having an active hydrogen,

(ii) addition of the mixture from step (i) to a support material, and

(iii) addition of a transition metal compound in a suitable solvent.

The cation of the ionic activator may be selected from the groupconsisting of acidic cations, carbonium cations, silylium cations,oxonium cations, organometallic cations and cationic oxidizing agents.

Suitably preferred cations include trihydrocarbyl substituted ammoniumcations eg. triethylammonium, tripropylammonmoium, tri(n-butyl) ammoniumand similar. Also suitable are N.N-dialkylammonium cations such asN,N-dimethylanilinium cations.

Particularly suitable are those cations having longer alkyl chains suchas dihexyldecylmethylammonium, dioctadecylmethylammonium,ditetradecylmethylammonium, bis(hydrogenated tallow alkyl)methylammonium and similar.

Examples of suitable anions include:

-   -   triphenyl(hydroxyphenyl)borate    -   tri(p-tolyl)(hydroxyphenyl)borate    -   tris(pentafluorophenyl)(hydroxyphenyl)borate    -   tris(pentafluorophenyl)(4-hydroxyphenyl)borate

Particular preferred ionic activators are alkylammoniumtris(pentafluorophenyl)4-(hydroxyphenyl)borates. A particularlypreferred activator is bis(hydrogenated tallow alkyl)methyl ammoniumtris(pentafluorophenyl)(4-hydroxyphenyl)borate.

Suitable activators of this type are described in WO 98/27119 therelevant portions of which are incorporated herein by reference.

Particular preferred ionic activators are alkylammoniumtris(pentafluorophenyl)4-(hydroxyphenyl)borates. A particularlypreferred activator is bis(hydrogenated tallow alkyl)methyl ammoniumtris(pentafluorophenyl)(4-hydroxyphenyl)borate.

Aluminoxanes are well known in the art and preferably compriseoligomeric linear and/or cyclic alkyl aluminoxanes. Aluminoxanes may beprepared in a number of ways and preferably are prepare by contactingwater and a trialkylaluminium compound, for example trimethylaluminum,in a suitable organic medium such as benzene or an aliphatichydrocarbon.

The preferred aluminoxane is tetraisobutyaluminoxane.

The preferred molar ratio of the aluminoxane (aluminium) to ionicactivator (boron) is typically in the range 20:0.1 and preferably in therange 10:0.2.

Suitable solvents for use in the present invention include alkanes egisohexane or cyclohexane or aromatic solvents eg—toluene.

According to another aspect of the present invention there is provided acatalyst component comprising the reaction product of

-   -   (a) an aluminoxane and    -   (b) an ionic activator comprising a cation and an anion wherein        the anion has at least one substituent comprising a moiety        having an active hydrogen,

Suitable transition metal compounds may be those based on the latetransition metals (LTM) of Group VIII for example compounds containingiron, nickel, manganese, ruthenium, cobalt or palladium metals. Examplesof such compounds are described in WO 98/27124 and WO 99/12981 and maybe illustrated by [2,6-diacetylpyridinebis(2,6-diisopropylanil)FeCl₂],2.6-diacetylpyridinebis(2,4,6-trimethlylanil)FeCl₂, and[2,6-diacetylpyridinebis(2,6-diisopropylanil)CoCl₂].

Other catalysts include derivatives of Group IIIA, IVA or Lanthanidemetals which are in the +2, +3 or +4 formal oxidation state. Preferredcompounds include metal complexes containing from 1 to 3 anionic orneutral ligand groups which may be cyclic or non-cyclic delocalizedπ-bonded anionic ligand groups. Examples of such π-bonded anionic ligandgroups are conjugated or non-conjugated, cyclic or non-cyclic dienylgroups, allyl groups, boratabenzene groups, phosphole and arene groups.By the term π-bonded is meant that the ligand group is bonded to themetal by a sharing of electrons from a partially delocalised π-bond.

Each atom in the delocalized π-bonded group may independently besubstituted with a radical selected from the group consisting ofhydrogen, halogen, hydrocarbyl, halohydrocarbyl, hydrocarbyl,substituted metalloid radicals wherein the metalloid is selected fromGroup IVB of the Periodic Table. Included in the term “hydrocarbyl” areC1-C20 straight, branched and cyclic alkyl radicals, C6-C20 aromaticradicals, etc. In addition two or more such radicals may together form afused ring system or they may form a metallocycle with the metal.

Examples of suitable anionic, delocalised π-bonded groups includecyclopentadienyl, indenyl, fluorenyl, tetrahydroindenyl,tetrahydrofluorenyl, octahydrofluorenyl, etc. as well as phospholes andboratabenzene groups.

Phospholes are anionic ligands that are phosphorus containing analoguesto the cyclopentadienyl groups. They are known in the art and describedin WO 98/50392.

The boratabenzenes are anionic ligands that are boron containinganalogues to benzene. They are known in the art and are described inOrganometallics, 14, 1, 471-480 (1995).

The preferred polymerisation catalyst of the present invention is abulky ligand compound also referred to as a metallocene complexcontaining at least one of the aforementioned delocalized π-bondedgroup, in particular cyclopentadienyl ligands. Such metallocenecomplexes are those based on Group IVA metals for example titanium,zirconium and hafnium.

Metallocene complexes may be represented by the general formula:LxMQnwhere L is a cyclopentadienyl ligand, M is a Group IVA metal, Q is aleaving group and x and n are dependent upon the oxidation state of themetal.

Typically the Group IVA metal is titanium, zirconium or hafnium, x iseither 1 or 2 and typical leaving groups include halogen or hydrocarbyl.The cyclopentadienyl ligands may be substituted for example by alkyl oralkenyl groups or may comprise a fused ring system such as indenyl orfluorenyl.

Examples of suitable metallocene complexes are disclosed in EP 129368and EP 206794. Such complexes may be unbridged eg.bis(cyclopentadienyl)zirconium dichloride,bis(pentamethyl)cyclopentadienyl dichloride, or may be bridged eg.ethylene bis(indenyl)zirconium dichloride ordimethylsilyl(indenyl)zirconium dichloride.

Other suitable bis(cyclopentadienyl)metallocene complexes are thosebis(cyclopentadienyl)diene complexes described in WO 96/04290. Examplesof such complexes arebis(cyclopentadienyl)zirconium(2.3-dimethyl-1,3-butadiene) and ethylenebis(indenyl)zirconium 1,4-diphenyl butadiene.

Examples of monocyclopentadienyl or substituted monocyclopentadienylcomplexes suitable for use in the present invention are described in EP416815, EP 418044, EP 420436 and EP 551277. Suitable complexes may berepresented by the general formula:CpMX_(n)wherein Cp is a single cyclopentadienyl or substituted cyclopentadienylgroup optionally covalently bonded to M through a substituent, M is aGroup VIA metal bound in a η⁵ bonding mode to the cyclopentadienyl orsubstituted cyclopentadienyl group, X each occurrence is hydride or amoiety selected from the group consisting of halo, alkyl, aryl, aryloxy,alkoxy, alkoxyalkyl, amidoalkyl, siloxyalkyl etc. having up to 20non-hydrogen atoms and neutral Lewis base ligands having up to 20non-hydrogen atoms or optionally one X together with Cp forms ametallocycle with M and n is dependent upon the valency of the metal.

Particularly preferred monocyclopentadienyl complexes have the formula:

wherein:—

-   -   R′ each occurrence is independently selected from hydrogen,        hydrocarbyl, silyl, germyl, halo, cyano., and combinations        thereof, said R′ having up to 20 nonhydrogen atoms, and        optionally, two R′ groups (where R′ is not hydrogen, halo or        cyano) together form a divalent derivative thereof connected to        adjacent positions of the cyclopentadienyl ring to form a fused        ring structure;    -   X is hydride or a moiety selected from the group consisting of        halo, alkyl, aryl, aryloxy, alkoxy, alkoxyalkyl, amidoalkyl,        siloxyalkyl etc. having up to 20 non-hydrogen atoms and neutral        Lewis base ligands having up to 20 non-hydrogen atoms,    -   Y is —O—, —S—, —NR*—, —PR*—,    -   M is hafnium, titanium or zirconium,    -   Z* is SiR*₂, CR*₂, SiR*₂SIR*₂, CR*₂CR*₂, CR*═CR*, CR*₂SIR*₂, or    -   GeR*₂, wherein:

R* each occurrence is independently hydrogen, or a member selected fromhydrocarbyl, silyl, halogenated alkyl, halogenated aryl, andcombinations thereof, said

R* having up to 10 non-hydrogen atoms, and optionally, two R* groupsfrom Z* (when R* is not hydrogen), or an R* group from Z* and an R*group from Y form a ring system,

and n is 1 or 2 depending on the valence of M.

Examples of suitable monocyclopentadienyl complexes are(tert-butylamido)dimethyl(tetramethyl-η⁵-cyclopentadienyl)silanetitaniumdichloride and(2-methoxyphenylamido)dimethyl(tetramethyl-η⁵-cyclopentadienyl)silanetitaniumdichloride.

Other suitable monocyclopentadienyl complexes are those comprisingphosphinimine ligands described in WO 99/40125, WO 00/05237, WO 00/05238and WO00/32653. A typical examples of such a complex is cyclopentadienyltitanium[tri(tertiary butyl)phosphinimine]dichloride.

Another type of polymerisation catalyst suitable for use in the presentinvention are monocyclopentadienyl complexes comprising heteroallylmoieties such as zirconium(cyclopentadienyl)tris(diethylcarbamates) asdescribed in U.S. Pat. No. 5,527,752 and WO 99/61486.

Particularly preferred metallocene complexes for use in the preparationof the supported catalysts of the present invention may be representedby the general formula:

wherein:—

-   -   R′ each occurrence is independently selected from hydrogen,        hydrocarbyl, silyl, germyl, halo, cyano, and combinations        thereof, said R′ having up to 20 nonhydrogen atoms, and        optionally, two R′ groups (where R′ is not hydrogen, halo or        cyano) together form a divalent derivative thereof connected to        adjacent positions of the cyclopentadienyl ring to form a fused        ring structure;    -   X is a neutral η⁴ bonded diene group having up to 30        non-hydrogen atoms, which forms a π-complex with M;    -   Y is —O—, —S—, —NR*—, —PR*—,    -   M is titanium or zirconium in the +2 formal oxidation state;    -   Z* is SiR*₂, CR*₂, SiR*₂SIR*₂, CR*₂CR*₂, CR*═CR*, CR*₂SIR*₂, or    -   GeR*₂, wherein:

R* each occurrence is independently hydrogen, or a member selected fromhydrocarbyl, silyl, halogenated alkyl, halogenated aryl, andcombinations thereof, said

R* having up to 10 non-hydrogen atoms, and optionally, two R* groupsfrom Z* (when R* is not hydrogen), or an R* group from Z* and an R*group from Y form a ring system.

Examples of suitable X groups includes-trans-η⁴-1,4-diphenyl-1,3-butadiene,s-trans-η⁴-3-methyl-1,3-pentadiene; s-trans-η⁴-2,4-hexadiene;s-trans-η⁴-1,3-pentadiene; s-trans-η⁴-1,4-ditolyl-1,3-butadiene;s-trans-η⁴-1,4-bis(trimethylsilyl)-1,3-butadiene;s-cis-η⁴-3-methyl-1,3-pentadiene; s-cis-η⁴-1,4-dibenzyl-1,3-butadiene;s-cis-η⁴-1,3-pentadiene; s-cis-η⁴-1,4-bis(trimethylsilyl)-1,3-butadiene,said s-cis diene group forming a η-complex as defined herein with themetal.

Most preferably R′ is hydrogen, methyl, ethyl, propyl, butyl, pentyl,hexyl, benzyl, or phenyl or 2 R′ groups (except hydrogen) are linkedtogether, the entire C₅R′₄ group thereby being, for example, an indenyl,tetrahydroindenyl, fluorenyl, tetrahydrofluorenyl, or octahydrofluorenylgroup.

Highly preferred Y groups are nitrogen or phosphorus containing groupscontaining a group corresponding to the formula-N(R″)- or-P(R″)- whereinR″ is C₁₋₁₀ hydrocarbyl.

Most preferred complexes are amidosilane- or amidoalkanediyl complexes.

Most preferred complexes are those wherein M is titanium.

Specific complexes suitable for use in the preparation of the supportedcatalysts of the present invention are those disclosed in WO 95/00526and are incorporated herein by reference.

A particularly preferred complex for use in the preparation of thesupported catalysts of the present invention is(t-butylamido)(tetramethyl-η⁵-cyclopentadienyl)dimethylsilanetitanium-72⁴-1,3-pentadiene.

Suitable support materials include inorganic metal oxides oralternatively polymeric supports may be used.

The most preferred support material for use with the supported catalystsaccording to the process of the present invention is silica. Suitablesilicas include Ineos ES70 and Grace-Davison 948 silicas.

The support material may be subjected to a heat treatment and/orchemical treatment to reduce the water content or the hydroxyl contentof the support material. Typically chemical dehydration agents arereactive metal hydrides, aluminium alkyls and halides. Prior to its usethe support material may be subjected to treatment at 100° C. to 1000°C. and preferably at 200 to 850° C. in an inert atmosphere under reducedpressure.

The support material may be further combined with an organometalliccompound preferably an organoaluminium compound and most preferably atrialkylaluminium compound in a dilute solvent.

A particularly preferred trialkyl aluminium compound for use in thepresent invention is triisobuylaluminium.

The support material is pretreated with the organometallic compound at atemperature of −20° C. to 150° C. and preferably at 20° C. to 100° C.

In a preferred process according to the present invention, the supportedcatalyst is prepared by use of a one-pot procedure. This allows for amore efficient procedure as well as having economic benefits.

By one-pot is meant a preparation carried out without the need forwashing steps and typically wherein the contact between the supportmaterial, ionic activator and metallocene is performed in a singlereaction vessel.

The one-pot procedure may also incorporate a final precipitation step,using for example the addition of hexane to the mixture resulting fromstep (iii). In this procedure a slurry or mud of the catalyst isobtained which may be used directly to inject the catalyst into thepolymerisation reactor.

The molar ratio of transition metal compound to ionic activator employedin the method of the present invention may be in the range 1:10000 to100:1. A preferred range is from 1:5000 to 10:1 and most preferred from1:10 to 10:1.

The supported transition metal catalysts of the present invention may besuitable for the polymerisation of olefin monomers selected from (a)ethylene, (b) propylene (c) mixtures of ethylene and propylene and (d)mixtures of (a), (b) or (c) with one or more other alpha-olefins.

Thus according to another aspect of the present invention there isprovided a process for the polymerisation of olefin monomers selectedfrom (a) ethylene, (b) propylene (c) mixtures of ethylene and propyleneand (d) mixtures of (a), (b) or (c) with one or more otheralpha-olefins, said process performed in the presence of a supportedtransition metal catalyst system as hereinbefore described.

The process of the present invention may be directed to the solution,slurry or gas phase.

A slurry process typically uses an inert hydrocarbon diluent andtemperatures from about 0° C. up to a temperature just below thetemperature at which the resulting polymer becomes substantially solublein the inert polymerisation medium. Suitable diluents include toluene oralkanes such as hexane, propane or isobutane. Preferred temperatures arefrom about 30° C. up to about 200° C. but preferably from about 60° C.to 100° C. Loop reactors are widely used in slurry polymerisationprocesses.

The preferred process for the present invention is the gas phase.

Suitable gas phase processes of the present invention include thepolymerisation of olefins, especially for the homopolymerisation and thecopolymerisation of ethylene and α-olefins for example 1-butene,1-hexene, 4-methyl-1-pentene are well known in the art. Particularlypreferred gas phase processes are those operating in a fluidised bed.Examples of such processes are described in EP 89691 and EP 699213 thelatter being a particularly preferred process for use with the supportedcatalysts of the present invention.

Particularly preferred polymerisation processes are those comprising thepolymerisation of ethylene or the copolymerisation of ethylene andα-olefins having from 3 to 10 carbon atoms.

Thus according to another aspect of the present invention there isprovided a process for the polymerisation of ethylene or thecopolymerisation of ethylene and α-olefins having from 3 to 10 carbonatoms, said process performed under polymerisation conditions in thepresent of a supported metallocene catalyst system prepared ashereinbefore described.

The present invention will now be further illustrated with reference tothe following examples:

Abbreviations

TEA triethylaluminium

TiBAO tetraisobutylaluminoxane

TiBA triisobutylaluminium

Ionic Activator A [N(H)Me(C₁₈₋₂₂H₃₇₋₄₅)₂][B(C₆F₅)₃(C₆H₄OH)]

Complex A (C₅Me₄SiMe₂N^(t)Bu)Ti(η⁴-1,3-pentadiene)

EXAMPLE 1

Catalyst Preparation

To 3 g. of Ineos ES70 silica (previously calcined at 500° C. for 5 hoursunder nitrogen, pore volume 1.55 ml/g) was added a solution made with2.81 ml of a hexane solution of triisobutylaluminium (TiBA), 0.96 mol/Land 1.84 ml of hexane. The mixture was allowed to react for 2.5 hoursunder agitation then dried under vacuum.

1.51 ml of Ionic Activator A (previously dried by prolonged contact withmolecular sieves 4A) was reacted with 0.31 ml. of TiBAO solution incyclohexane (0.812 mol/L) (molar ratio of TiBAO/activator=2; Al/Bratio=4).

1.82 ml of this solution was slowly impregnated (15 min) to the aboveTiBA treated silica and manually agitated until no lumps were visible.The solution was held for 30 min.

0.72 ml of Complex A solution in heptane (9.17% wt) was then slowlyadded (15 min) and manually agitated until no lumps were visible. Thensolution was held for 60 min. and then the catalyst dried under vacuum.

The resultant catalyst had [Ti]=40 μmol/g and [Al]=0.83 mmol/g.

EXAMPLE 2

Catalyst Preparation

The procedure of Example 1 was repeated except that the final driedcatalyst was reslurried in hexane in an amount of 2.5 ml hexane to 1 gof catalyst followed by holding for 45 min. after which time thecatalyst was dried under vacuum.

EXAMPLE 3

Polymerisation Data

The catalysts from Examples 1 and 2 were tested for ethylene-1-hexenecopolymerisation as follows:

A 2.5 1 double jacketed thermostatic stainless steel autoclave waspurged with nitrogen at 70° C. for at least one hour. 200 g of PEpellets previously dried under vacuum at 80° C. for 12 hours wereintroduced and the reactor was then purged three times with nitrogen (7bar to atmospheric pressure). ˜0.13 g of TEA treated silica (1.5 mmolTEA/g) was added under pressure and allowed to scavenge impurities forat least 15 minutes under agitation. The gas phase was then composed(addition of ethylene, 1-hexene and hydrogen) and a mixture of supportedcatalyst (˜0.1 g) and silica/TEA (˜0.1 g) was injected. A constantpressure of ethylene and a constant pressure ratio ofethylene/co-monomer were maintained during the run. The run wasterminated by venting the reactor and then purging the reactor 3 timeswith nitrogen. The PE powder produced during the run was then separatedfrom the PE seed bed by simple sieving.

Typical conditions are as follows:

Temperature: 70° C.

Ethylene pressure: 6.5 b

P(1-hexene)/P(ethylene): 0.004-0.008

Hydrogen: 70-100 ml added during the gas phase composition AverageActivity Activity at 1 h Catalyst (g/g · h · bar) (g/g · h · bar)Example 1 63 50 Example 2 60 40

Both the catalysts from the present invention showed low decay activityprofiles.

The polymer from Example 2 had the following properties:

MI(2.16)=1 g/10 min.

Density=0.921 g/ml

Melt strength(16 Mpa) 5.9 cN

A low exotherm (56° C./g catalyst) was observed compared with a typicaltemperature in the region of 150° C./g catalyst for prior art catalysts.

1. A method for the preparation of a supported transition metal catalystsystem, the method comprising the steps of: (i) mixing together in asuitable solvent (a) an aluminoxane and (b) an ionic activator having acation and an anion, wherein the anion has at least one substituentcontaining a moiety having an active hydrogen, (ii) adding the mixturefrom step (i) to a support material, and (iii) adding a transition metalcompound in a suitable solvent.
 2. The method according to claim 1,wherein the ionic activator is an alkylammoniumtris(pentafluorophenyl)(4-hydroxyphenyl)borate.
 3. The method accordingto claim 1, wherein the aluminoxane is tetraisobutyldialuminoxane. 4.The method according to claim 2, wherein the molar ratio of thealuminoxane (aluminium) to ionic activator (boron) is in the range20:0.1.
 5. The method according to claim 1, wherein the support materialis silica.
 6. The method according to claim 5, wherein the silica ispretreated with an organoaluminium compound.
 7. The method according toclaim 6, wherein the organoaluminium compound is triisobutylaluminium.8. The method according to claim 1, wherein the transition metalcompound is a metallocene.
 9. The method according to claim 8, whereinthe metallocene has the formula:CpMX_(n) wherein Cp is a single cyclopentadienyl or substitutedcyclopentadienyl group optionally covalentyl bonded to M through asubstituent, M is a Group VIA metal bound in a η⁵ bonding mode to thecyclopentadienyl or substituted cyclopentadienyl group, X each occuranceis hydride or a moiety selected from the group consisting of halo,alkyl, aryl, aryloxy, alkoxy, alkoxyalkyl, amidoalkyl, and siloxyalkylhaving up to 20 non-hydrogen atoms and neutral Lewis base ligands havingup to 20 non-hydrogen atoms or optionally one X together with Cp forms ametallocycle with M and n is dependent upon the valency of the metal.10. The method according to claim 8, wherein the metallocene isrepresented by the general formula:

wherein: R′ each occurrence is independently selected from the groupconsisting of hydrogen, hydrocarbyl, silyl, germyl, halo, cyano, andcombinations thereof, said R′ having up to 20 nonhydrogen atoms, andoptionally, two R′ groups (where R′ is not hydrogen, halo or cyano)together form a divalent derivative thereof connected to adjacentpositions of the cyclopentadienyl ring to form a fused ring structure; Xis a neutral η⁴ bonded diene group having up to 30 non-hydrogen atoms,which forms a π-complex with M; Y is —O—, —S—, —NR*—, or —PR*—, M istitanium or zirconium in the +2 formal oxidation state; Z* is SiR*₂,CR*₂, SiR*₂SIR*₂, CR*₂CR*₂, CR*═CR*, CR*₂SIR*₂, or GeR*₂, wherein: R*each occurrence is independently hydrogen, or a member selected from thegroup consisting of hydrocarbyl, silyl, halogenated alkyl, halogenatedaryl, and combinations thereof, said R* having up to 10 non-hydrogenatoms, and optionally, two R* groups from Z* (when R* is not hydrogen),or an R* group from Z* and an R* group from Y form a ring system.
 11. Aprocess for the polymerisation of olefin monomers, comprisingpolymerising an olefin monomer selected from the group consisting of (a)ethylene, (b) propylene (c) mixtures of ethylene and propylene and (d)mixtures of (a), (b) or (c) with one or more other alpha-olefins underpolymerisation conditions and in the presence of a supported transitionmetal catalyst system prepared by: (i) mixing together in a suitablesolvent (a) an aluminoxane and (b) an ionic activator having a cationand an anion, wherein the anion has at least one substituent containinga moiety having an active hydrogen. (ii) adding the mixture from step(i) to a support material, and (iii) adding a transition metal compoundin a suitable solvent.
 12. A process for the (co-)polymerization ofethylene, comprising polymerising ethylene or copolymerising ethyleneand α-olefins having from 3 to 10 carbon atoms, under polymerisationconditions and in the presence of a supported catalyst system preparedby: (i) mixing together in a suitable solvent (a) an aluminoxane and (b)an ionic activator having a cation and an anion, wherein the anion hasat least one substituent containing a moiety having an active hydrogen.(ii) adding the mixture from step (i) to a support material, and (iii)adding a transition metal compound in a suitable solvent.
 13. Theprocess according to claim 12, wherein the α-olefin is 1-butene,1-hexene, 4-methyl-1-pentene or 1-octene.
 14. The process according toclaim 11 or 12, wherein the process is performed in the solution, slurryor gas phase.
 15. The process according to claim 14, wherein the processis performed in a fluidised bed gas phase reactor.
 16. A catalystcomponent comprising the reaction product of (a) an aluminoxane and (b)an ionic activator having a cation and an anion, wherein the anion hasat least one substituent containing a moiety having an active hydrogen.17. The catalyst component according to claim 16, wherein the ionicactivator is an alkylammoniumtris(pentafluorophenyl)(4-hydroxyphenyl)borate.
 18. The catalystcomponent according to claim 16, wherein the aluminoxane istetraisobutyldialuminoxane.